Clamp lift and cycle starting control system for sewing machines



p 0, 968 J. A. RAIQJDONIS, JR 3,400,676

CLAMP LIFT AND CYCLE STARTING CONTROL SYSTEM FOR SEWING MACHINES Filed June 8, 1967 STITCH FORMING STITCH FORMING Fug. 3

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INVENTOR. John A. RoudonisJR.

I BY

WIITN S: W A TORNEY United States Patent M 3,400,676 CLAMP LIFT AND CYCLE STARTING CONTROL SYSTEM FOR SEWING MACHINES John A. Randonis, Jr., Elizabeth, N.J., assignor to The Singer Company, New York, N.Y., a corporation of New Jersey Filed June 8, 1967, Ser. No. 644,656 2 Claims. (Cl. 112-67) ABSTRACT OF THE DISCLOSURE A fluid operated control system for initiating the cycle starting and lifting of the Work clamp of a cyclic sewing machine is disclosed in which a normally closed time delayed opening interlock valve controls the initiation of the cycle starting.

SUMMARY OF THE INVENTION This invention relates to operator assist devices for controlling the cycle starting of sewing machines as well as the operation of devices ancillary to the sewing instrumentalities such as the lifting and lowering of a work holding clamp.

A problem which arises with such control devices is that of providing practical and effective interlock to prevent initiation of the cycle starting operation of the control device until the work clamp has attained a fully lowered condition and is in readiness for the sewing cycle.

In the prior art a number of expedients are known for preventing cycle starting while the work clamp is being held completely open. The US. Patent No. 2,764,112, September 25, 1965 to R. Happe discloses one such expedient wherein different positions of a single operator influenced lever control clamp lifting and cycle starting in a manner such that these two functions cannot occur simultaneously. Furthermore, mechanical interlocks are conventionally included within the sewing machine for preventing starting when the work clamp occupies an open position. While such mechanical interlocks operate completely satisfactorily when the work clamp is fully open, they are subject to abnormal wear and malfunction if they are relied upon to prevent cycle starting while the work clamp is being lowered i.e., during the actual disengaging movement of the mechanical interlock.

The US. Patent No. 3,298,341, Jan. 17, 1967 of Bonis discloses an interlock for preventing cycle starting until a control piston for lifting a work clamp has been retracted. The control piston, however, is remote from the work clamp and therefore, when the control piston is retracted, the work clamp is not necessarily completely lowered. Moreover, the Bonis patent presupposes that the work clamp lifting linkage of the sewing machine is positive acting in both directions whereas in fact, work clamp lifting linkages are conventionally positive acting only to lift or open the work clamp. The lifting linkage is conventionally made separable from the work clamp so that the work clamp can accommodate varying thicknesses of work fabric without conflict with the Work clamp lifting controls.

The present invention provides a fluid operated control system for lifting the work clamp and initiating cycle starting of a sewing machine in which different positions ofan operator influenced lever control alternatively the clamp lifting and cycle starting functions so that the two cannot occur simultaneously. This invention solves the 3,400,676 Patented Sept. 10, 1968 problem of preventing initiation of the cycle starting function of the control system until the work clamp has attained a fully lowered condition by the provision in the fluid supply line to the cycle starting cylinder of a normally closed time delay opening valve for which the time delay may be preselected to concide with that necessary for the work clamp to attain completely lowered condit1on.

DESCRIPTION OF THE DRAWINGS With the above and additional objects and advantages in view as will hereinafter appear this invention will be described below with reference to the accompanying drawing of a preferred embodiment in which:

FIG. 1 is a diagrammatic view of a sewing machine control system embodying this invention with the elements of the system illustrated in a condition in which the sewing machine is stopped and the sewing machine work clamp is being held open by the control system,

FIG. 2 is a view like FIG. 1 but with the elements of the system illustrated in a condition in which the sewing machine is stopped and the work clamp is closed, and

FIG. 3 is a view like FIG. 1 but with the elements of the system illustrated in a condition in which cycle starting of the sewing machine is initiated by the control system.

DETAILED DESCRIPTION The control system of this invention is illustrated in the accompanying drawing as applied to a conventional cyclic sewing machine which includes a needle 11 which is adapted to be reciprocated relatively to a work support 12 by a drive shaft 13. Indicated generally at 14 are stitch forming instrumentalities also adapted to be actuated by the drive shaft 13 in timed relation with the needle. A work clamp 15 is shiftable supported on the sewing machine for movement into and out of a work clamping position contiguous to the sewing machine work support 12 and biased into work clamping position by a spring 16. A work clamp lifting linkage is represented by a lever 17 fulcrumed on the sewing machine.

The driving mechanism of the sewing machine includes a driven clutch element 20 on the drive shaft 13, and a driving clutch element 21 operatively connected to a drive motor 22 and shiftable into and out of engagement with the driven clutch element 20 in response to movement of a control lever 23 fulcrumed on the sewing machine. A latch lug 24 on the control lever 23 is enga'geable by a latch element 25 for detaining the control lever 23 in the engaged condition of the clutch elements 20 and 21 until the latch element is released by conventional stop motion mechanism of the sewing machine after a stitching cycle of a predetermined number of stitches has been completed. A spring 26 biases the control lever 23 toward the declutched position of elements 20 and 21.

The control system of this invention utilizes a fluid pressure operated motor including a piston 30 movable in a cylinder 31 to raise and lower the Work clamp. A connecting rod 32 affixed to the piston is pivoted to the clamp operating lever 17 and a spring 33 acting upon the piston 30 biases the piston toward the lowered position of the work clamp. Another fluid pressure operated motor comprising a piston 35 movable in a cylinder 36 is utilized to initiate starting of a sewing cycle. A connecting rod 37 affixed to the piston 35 is pivoted to the control level 23 and a spring 38 acting upon the piston 35 biases the piston toward the declutched position of the elements 20 and 21.

While any fluid medium may be used to operate the control system of this invention the preferred form as illustrated in the drawing utilizes compressed air. From a source (not shown) compressed air admitted through a pressure regulating valve 39 to a conduit 40 leading to a normally open valve 41 operated by a plunger 42, and to a conduit 43 leading to a normally closed valve 44 operated by a plunger 45. Under the influence of a sewing machine operator, as by way of a treadle 46, or the like, is a valve control cam 47 adapted to engage the valve plungers 42 and 45. A spring 48 biases the treadle 46 into a first position illustrated in FIG. 1 in which the cam 47 is out of engagement with both valve plungers 42 and 45.

From the normally open valve 41, a conduit 50 is directed to a normally open valve 51 operated by a plunger 52 which is arranged in the path of a control cam 53 carried on the connecting rod 37 of the piston 35 which influences the initiation of sewing cycles. As illustrated in FIG. 1 when clutch elements and 21 of the sewing machine are disengaged and the piston 35 is biased into the returned position by the spring 38, the control cam 53 will be out of engagement with the plunger of the normally open valve 51 and a conduit 54 from the valve 51 to the cylinder 31 will direct compressed air from the source to the piston opening the work clamp 15.

FIG. 2 illustrates a second or intermediate position of the treadle 46 in which the control cam 47 associated therewith has been shifted int-o engagement with the plunger 42 to close the valve 41. No compressed air will be supplied to the cylinder 31 and the piston 30 will be returned by the spring 33 allowing the work clamp 15 to close. If the operator should then release the treadle 46 for return to the first position, the valve 41 will be reopened and the work clamp will be raised by the piston 30 as illustrated in FIG. 1. The transition as between the conditions illustrated in FIGS. 1 and 2 is reversible and the operator may open and close the work clamp as many times as is necessary until she is satisfied that work is properly orientated therein.

FIG. 3 illustrates the position of the parts after the operator has fully depressed the treadle 46 into the third position. The control cam 47 will then shift to a position engaging both plungers 42 and 45 thus holding closed the valve 41 to cut off compressed air from the work clamp opening cylinder 31 and opening the valve 44. A conduit 60 leads from the valve 44 to a normally closed time delay opening, three port, two position air valve indicated generally at 61. From the valve 61 a conduit 62 leads to the sewing cycle starting cylinder 36.

As illustrated diagrammatically in the drawing, the valve 61 is shiftable between two positions relatively to the conduits 60 and 62. A spring 63 normally biases the valve into a position illustrated in FIGS. 1 and 2 in which a chamber 64 occupies an effective position blocking passage between the conduits 60 and 62 and exhausting the conduit 62 to the atmosphere. A second position as illustrated in FIG. 3 is effected by an air cylinder 65 supplied from the conduit 60 by a conduit 66 having a throttle valve 67. The air cylinder 65 serves to shift a chamber 68 into an effective position in which the conduits 60 and 62 are in communication only after a time delay occasioned by filling of the air cylinder 65. The shiftable chamber 68 in conjunction with the air cylinder 65 constitutes an auxiliary fluid pressure operated motor for opening the valve 61 after a time delay. An adjustable plunger 69 is provided in the air cylinder 65 to vary the size of the reservoir represented by the air cylinder 65 thus to vary the time delay prior to opening of the conduits 60 and 62 to each other after admission of pressure to the conduit 60.

When air under pressure is admitted to the cylinder 36 by the delayed opening of the valve 61, the piston will be depressed shifting the sewing machine starting lever 23 into the running position illustrated in FIG. 3 in which position the latch 24, 25 will retain the parts until the sewing machine signals completion of a sewing cycle by releasing the latch. While the sewing machine is running the latch 24 and 25 will also hold the piston 35 depressed and the control cam 53 will be in engagement with the plunger 52 of the valve 51 holding the valve 51 closed. The operator, therefore, may release the treadle 46 for return by the spring 48 to the position illustrated in FIG. 1. The latch 24, 25 will maintain operation of the sewing machine and the control cam 53 will maintain the valve 51 closed to prevent opening of the work clamp despite the return of the valve 41 to the normally open position. Upon release of the treadle 46, the valve 44 will also return to the normally closed position and the time delay valve 61 will revert to the normally closed position illustrated in FIG. 1.

The plunger 69 is preferably adjusted so as to provide a time delay in the operation of the valve 61 which corresponds with the longest time necessary for the work clamp 15 to shift from a fully opened to a fully closed position.

Mechanical interlocks are conventional in cyclic sewing machines to prevent starting of a sewing cycle while the work clamp is opened. Such mechanical interlocks operate satisfactorily when they are fully engaged, as for instance, if a foreign object were to become wedged beneath the work clamp preventing closing. Mechanical interlocks, however, wear extremely rapidily and are subject to malfunction if they are relied upon during disengaging motion thereof. The valve 61 of this invention does not operate to prevent admission of compressed air to the cylinder 36 in the event that the work clamp is held completely opened as 'by a foreign object. The valve 61 does, however, prevent operation of the piston 35 to start the machine cycle while the work clamp is moving to the closed position. The valve 61 thus protects any mechanical interlock which may be incorporated in the sewing machine from undue wear and a consequent advantage of the control system of this invention is that it minimizes maintainence of the sewing machine.

Having thus set forth the nature of this invention, what I claim herein is:

1. In a cyclically operating sewing machine having a work holding clamp biased toward a closed position and shiftable to an opened position, a drive means including control mechanism shiftable from a non-operating position of said drive means to an operating position thereof, and latch means maintaining said control mechanism in said operating position for a predetermined cycle of sewing machine operation, an operators control movable from a normal first position through an intermediate second position to a third position, first fluid means connected to said operators control and to said work holding clamp for shifting said work holding clamp into an opened position in response to movement of the operators control into the first position and for relasing said work holding clamp for movement into a closed position in response to movement of the operators control into the intermediate position, second fluid means connected to said operators control and to said control mechanism for said drive means for shifting said control mechanism into an operating position of said drive means in response to movement of said operators control into said third position, and an adjustable normally closed time-delay opening valve means separate from said second fluid means and connected to said second fluid means for delaying for a preselectable time the shifting of said control mechanism for said drive means into an operating position in response to movement of said operators control into said third position.

2. A device as set forth in claim 1 in which said normally closed time-delay opening valve means includes an auxiliary fluid pressure operated motor and said second fluid means comprises a normally closed valve means, means effective in response to movement of said operators control for opening said normally closed valve means, a

fluid pressure operated motor means connected to said control mechanism for said drive means, a conduit leading from said normally closed valve means to said fluid pressure operated motor means, in which said normally closed time-delay opening valve means is arranged in said conduit, and in which the time-delay opening is effected by operation of said auxiliary fluid pressure operated motor in response to fluid pressure in said conduit between said time-delay opening valve and said normally closed fluid valve means.

References Cited UNITED STATES PATENTS PATRICK D. LAWSON, Primary Examiner.

H. H. HUNTER, Assistant Examiner. 

